Method for manufacturing semiconductor device, and film-forming device

ABSTRACT

A method for manufacturing a semiconductor device including a TiN film. The method comprises: supplying TiCl4 gas to a substrate; purging the TiCl4 gas; supplying NH3 gas to the substrate; purging the NH3 gas; and supplying an inhibitor that inhibits adsorption of TiCl4 or NH3 to the substrate. A plurality of cycles each including the supplying the TiCl4 gas, the purging the TiCl4 gas, the supplying the NH3 gas, and the purging the NH3 gas are performed, at least a part of the plurality of cycles includes the supplying the inhibitor, and after the supplying the inhibitor is performed, the supplying the TiCl4 gas or the supplying the NH3 gas is performed without purging the inhibitor, or, after purging the inhibitor for a shorter time than the purging the TiCl4 gas or the purging the NH3 gas, the supplying the TiCl4 gas or the supplying the NH3 gas is performed.

TECHNICAL FIELD

The present disclosure relates to a method for manufacturing a semiconductor device and a film-forming device.

BACKGROUND

A technique for forming a TiN film on a substrate using an atomic layer deposition (ALD) method, in which TiCl₄ gas and NH₃ gas are alternately supplied onto a substrate, is known (e.g., see Patent Document 1).

PRIOR ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Laid-open Patent Publication No. 2018-66050

SUMMARY Problems to Be Resolved by the Invention

The present disclosure provides a technique capable of adjusting a film formation amount of a TiN film.

Means for Solving the Problem

One aspect of the present disclosure provides a method for manufacturing a semiconductor device, which is a method for manufacturing a semiconductor device including a TiN film, the method comprising supplying TiCl₄ gas to a substrate, purging the TiCl₄ gas, supplying NH₃ gas to the substrate, purging the NH₃ gas, and supplying an inhibitor that inhibits adsorption of TiCl₄ or NH₃ to the substrate, wherein a plurality of cycles each including the supplying the TiCl₄ gas, the purging the TiCl₄ gas, the supplying the NH₃ gas, and the purging the NH₃ gas are performed, at least a part of the plurality of cycles includes the supplying the inhibitor, and after the supplying the inhibitor is performed, the supplying the TiCl₄ gas or the supplying the NH₃ gas is performed without purging the inhibitor, or, after purging the inhibitor for a shorter time than the purging the TiCl₄ gas or the purging the NH₃ gas, the supplying the TiCl₄ gas or the supplying the NH₃ gas is performed.

Effect of the Invention

According to the present disclosure, a film formation amount of a TiN film can be adjusted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an example of a gas supply sequence of a method of forming a TiN film according to an embodiment.

FIG. 2A is a process cross-sectional view illustrating an example of a method of forming a TiN film according to an embodiment.

FIG. 2B is a process cross-sectional view illustrating the example of the method of forming the TiN film according to the embodiment.

FIG. 2C is a process cross-sectional view illustrating the example of the method of forming the TiN film according to the embodiment.

FIG. 2D is a process cross-sectional view illustrating the example of the method of forming the TiN film according to the embodiment.

FIG. 2E is a process cross-sectional view illustrating the example of the method of forming the TiN film according to the embodiment.

FIG. 2F is a process cross-sectional view illustrating the example of the method of forming the TiN film according to the embodiment.

FIG. 2G is a process cross-sectional view illustrating the example of the method of forming the TiN film according to the embodiment.

FIG. 3 is a diagram illustrating another example of a gas supply sequence of a method of forming a TiN film according to an embodiment.

FIG. 4A is a process cross-sectional view illustrating another example of a method of forming a TiN film according to an embodiment.

FIG. 4B is a process cross-sectional view illustrating another example of the method of forming the TiN film according to the embodiment.

FIG. 4C is a process cross-sectional view illustrating another example of the method of forming the TiN film according to the embodiment.

FIG. 4D is a process cross-sectional view illustrating another example of the method of forming the TiN film according to the embodiment.

FIG. 4E is a process cross-sectional view illustrating another example of the method of forming the TiN film according to the embodiment.

FIG. 4F is a process cross-sectional view illustrating another example of the method of forming the TiN film according to the embodiment.

FIG. 4G is a process cross-sectional view illustrating another example of the method of forming the TiN film according to the embodiment.

FIG. 5 is a diagram illustrating still another example of a gas supply sequence of a method of forming a TiN film according to an embodiment.

FIG. 6 is a diagram illustrating an example of a film-forming device.

FIG. 7 is a diagram illustrating an example of simulation results of adsorption energy of an NH₃ inhibitor.

FIG. 8 is a diagram illustrating an example of simulation results of adsorption energy of a TiCl₄ inhibitor.

DETAILED DESCRIPTION

Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. The same or corresponding reference numerals are assigned to the same or corresponding members or parts among all of the accompanying drawings, and descriptions thereof will not be repeated.

[Method of Forming TiN Film]

A method of forming a titanium nitride (TiN) film according to an embodiment is, for example, a method of forming a TiN film on a substrate having a concave portion such as a trench, a hole, or the like on a surface using an atomic layer deposition (ALD) process, and the method is performed in a state in which the substrate having the concave portion is accommodated in a processing container. As the substrate, any substrate to which an ALD process can be applied can be widely used. The substrate to which the ALD process can be applied is, for example, a semiconductor substrate made of silicon and the like. Examples of the substrate may include, for example, a semiconductor substrate used for manufacturing a semiconductor device (e.g., a dynamic random access memory (DRAM)) having a capacitor electrode.

(Example Using NH₃ Inhibitor)

FIG. 1 is a diagram illustrating an example of a gas supply sequence of a method of forming a TiN film according to an embodiment. In the method of forming the TiN film illustrated in FIG. 1, a plurality of cycles each including processes S11 to S16 are performed. Process S11 is a process of supplying an NH₃ inhibitor that inhibits adsorption of NH₃. Process S12 is a process of adjusting an adsorption amount of the NH₃ inhibitor. Process S13 is a process of supplying the NH₃ to a substrate. Process S14 is a process of purging the NH₃. Process S15 is a process of supplying TiCl₄ to the substrate. Process S16 is a process of purging the TiCl₄.

FIGS. 2A to 2G are process cross-sectional views illustrating an example of a method of forming a TiN film according to an embodiment. FIGS. 2A to 2G illustrate a state in which a TiCl_(x) layer (x is 1 to 4) is formed on an outermost surface of a concave portion after the plurality of cycles each including processes S11 to S16 are performed from the imitation of the method of forming the TiN film. As illustrated in FIG. 2A, a target substrate 200 on which a TiN film is formed includes an insulating film 201 in which a concave portion 202 is formed. The insulating film 201 may be an SiO₂ film or an Al₂O₃ film.

Process S11 is performed after a process of supplying TiCl₄ and before a process of supplying NH₃. In process S11, as illustrated in FIG. 2A, an NH₃ inhibitor 204 that inhibits adsorption of NH₃ 205 is supplied to the substrate 200.

The NH₃ inhibitor preferably contains an organic compound having at least one of a C═O bond, an S═O bond, a CN ring, and a CO ring. The organic compound having at least one of the C═O bond, the S═O bond, the CN ring, and the CO ring has high adsorption energy on a surface of a TiCl_(x) layer, and thus the organic compound is likely to be adsorbed on the surface of the TiCl_(x) layer. Further, since an adsorption reaction on the surface of the TiCl_(x) layer is mass conservative, a reverse reaction is likely to occur, and removal of the organic compound is easy. For example, it is possible to remove the organic compound in process S16 of purging the TiCl₄. For this reason, the organic compound does not need to be removed using an etching process or the like and is easy to introduce. Further, the term “mass conservative” means that the NH₃ inhibitor is adsorbed on the surface of the TiCl_(x) layer without causing mass loss.

Further, the NH₃ inhibitor is preferably acetone (C₃H₆O), dimethyl sulfoxide (DMSO) (C₂H₆SO), tetrahydrofuran (THF) (C₄H₈O), pyridine (C₅H₅N), or a derivative thereof. These organic compounds have low raw material costs and are relatively safe. Further, these organic compounds have high vapor pressures and are easily gasified. Further, these organic compounds can be easily removed by purging. Further, adsorption energies of these organic compounds can be easily adjusted using steric hindrance due to introduction of side chains. Further, examples of a derivative of acetone may include ethylmethyl ketone (C₄H₈O) and diethyl ketone (C₅H₁₀O). Further, examples of a derivative of THF may include dimethyltetrahydrofuran (C₆H₁₂O).

The supply of the NH₃ inhibitor 204 may be performed in a dilution gas environment. For example, the NH₃ inhibitor 204 may be supplied after an inside of a processing container is replaced with a dilution gas. Further, for example, the dilution gas may be supplied into the processing container together with the NH₃ inhibitor 204. In this case, the NH₃ inhibitor 204 may be supplied while supplying the dilution gas into the processing container, or the dilution gas and the NH₃ inhibitor 204 may be mixed and then the NH₃ inhibitor 204 (mixed gas) diluted with the dilution gas may be supplied into the processing container. Examples of the dilution gas may include an inert gas such as nitrogen (N₂) gas, a rare gas, or the like, carbon dioxide (CO₂) gas, and carbon monoxide (CO) gas. The dilution gas preferably contains at least one type of gas selected from the group consisting of helium (He) gas, neon (Ne) gas, argon (Ar) gas, krypton (Kr) gas, xenon (Xe) gas, N₂ gas, CO₂ gas, and CO gas.

In process S11, since the NH₃ inhibitor 204 is adsorbed on a surface of a TiCl_(x) layer 203 formed in the concave portion 202, it is preferable that the NH₃ inhibitor 204 is easily adsorbed on the TiCl_(x) layer 203. The organic compound having at least one of a C═O bond, an S═O bond, a CN ring, and a CO ring has high adsorption energy on the surface of the TiCl_(x) layer 203. For this reason, as illustrated in FIG. 2B, the organic compound is more likely to be adsorbed on an upper surface 202 c of the concave portion 202 than on a bottom surface 202 a and an inner wall 202 b thereof.

The likelihood of the adsorption of the NH₃ inhibitor 204 on the TiCl_(x) layer 203 can be predicted, for example, by evaluating an adsorption energy (hereinafter referred to as a “first adsorption energy”) of the NH₃ inhibitor 204 on the surface (surface site) of the TiCl_(x) layer 203. Further, the “first adsorption energy” is given as a value obtained by subtracting energy before the adsorption from energy when the NH₃ inhibitor 204 is adsorbed on the surface site, and a negative value indicates that the adsorption state is stable. Further, the larger the first adsorption energy (negative value), the easier it is for the NH₃ inhibitor 204 to be adsorbed on the surface site, and the stronger an adsorption force is. The first adsorption energy is obtained by, for example, a density functional theory (PBE/DNP) using the DMol3 module of the software Materials Studio.

In process S12, a purge gas is supplied into the processing container. Thereby, an amount of the NH₃ inhibitor 204 adsorbed on the TiCl_(x) layer 203 is adjusted. Specifically, by supplying the purge gas into the processing container, a part of the NH₃ inhibitor 204 adsorbed on the surface of the TiCl_(x) layer 203 is removed together with the purge gas, and thus the amount of the NH₃ inhibitor 204 adsorbed on the TiCl_(x) layer 203 is adjusted. In order to prevent the NH₃ inhibitor 204 adsorbed on the surface of the TiCl_(x) layer 203 from being completely removed, a time of process S12 of adjusting the adsorption amount of the NH₃ inhibitor 204 is preferably shorter than a time of process S14 of purging the NH₃. Further, when it is not necessary to adjust the amount of the NH₃ inhibitor 204 adsorbed on the TiCl_(x) layer 203, process S12 may be omitted. Examples of the purge gas may include an inert gas such as N₂ gas, a rare gas, or the like, CO₂ gas, and CO gas. Conditions for supplying the purge gas in process S12 are not particularly limited.

Further, process S12 may be performed by, for example, vacuum suctioning the inside of the processing container without supplying the purge gas into the processing container. Further, process S12 may be performed by supplying the purge gas into the processing container and then vacuum suctioning the inside of the processing container without supplying the purge gas into the processing container. Further, process S12 may be performed by a cycle purge in which the supply of the purge gas and the vacuum suction are repeated.

In process S13, the NH₃ 205 is supplied to the concave portion 202, as illustrated in FIG. 2C. In this case, since a greater amount of the NH₃ inhibitor 204 is adsorbed on the upper surface 202 c of the concave portion 202 than on the bottom surface 202 a and the inner wall 202 b thereof, a part of the adsorption of the NH₃ 205 on the upper surface 202 c of the concave portion 202 is inhibited, as illustrated in FIG. 2D. For this reason, the NH₃ 205 is adsorbed on the bottom surface 202 a, the inner wall 202 b, and the upper surface 202 c of the concave portion 202 substantially uniformly.

In process S14, the purge gas is supplied into the processing container. Thereby, as illustrated in FIG. 2E, the NH₃ inhibitor 204 adsorbed on the surface of the TiCl_(x) layer 203 and the NH₃ 205 remaining in the processing container are exhausted and removed from the inside of the processing container. Details of the purge gas and conditions for supplying the purge gas in process S14 may be the same as those in process S12 described above.

In process S15, TiCl₄ 206 is supplied to the concave portion 202, as illustrated in FIG. 2F. Thereby, as illustrated in FIG. 2G, the NH₃ 205 adsorbed on the concave portion 202 and the TiCl₄ 206 supplied to the concave portion 202 react with each other, and thus a TiN layer 207 is formed.

In process S16, the purge gas is supplied into the processing container. Thereby, the TiCl₄ 206 remaining in the processing container is removed from the inside of the processing container. Specifically, by supplying the purge gas into the processing container, the TiCl₄ 206 in the processing container is exhausted together with the purge gas and removed from the inside of the processing container. Details of the purge gas and conditions for supplying the purge gas in process S16 may be the same as those in process S12 described above.

As described above, in the method of forming the TiN film according to the embodiment, before the NH₃ 205 is supplied to the concave portion 202, a greater amount of the NH₃ inhibitor 204 is adsorbed on an upper portion of the concave portion 202 than on a lower portion thereof. In the case in which a greater amount of the NH₃ inhibitor 204 is adsorbed on the upper portion of the concave portion 202 than on the lower portion thereof, when the NH₃ 205 is supplied to the concave portion 202, the adsorption of the NH₃ 205 onto the upper surface 202 c of the concave portion 202 is inhibited. For this reason, the NH₃ 205 is adsorbed on the bottom surface 202 a, the inner wall 202 b, and the upper surface 202 c of the concave portion 202 substantially uniformly. As a result, a thickness of the TiN layer 207 formed by reacting the NH₃ 205 and the TiCl₄ 206 becomes uniform. That is, a conformal TiN film can be formed in the concave portion 202.

Further, the method of forming the TiN film according to the embodiment can be suitably used in, for example, an application for forming a capacitor electrode. In particular, in a semiconductor device having a memory cell such as a DRAM or the like, due to complexity of the trench structure and an increase in aspect ratio of a trench, the step coverage of the TiN film has become an important issue. Therefore, according to the method of forming the TiN film according to the embodiment, ideal conformal film formation with high step coverage and a low loading effect is possible.

Further, although the case in which all of the plurality of cycles include process S11 of supplying the NH₃ inhibitor 204 is illustrated in the example of FIG. 1, the present disclosure is not limited thereto. For example, at least a part of the plurality of cycles may include process S11 of supplying the NH₃ inhibitor 204. In other words, in at least a part of the plurality of cycles, process S11 of supplying the NH₃ inhibitor 204 may be omitted. However, from the viewpoint of obtaining a more conformal TiN film, it is preferable to perform process S11 of supplying the NH₃ inhibitor 204 in all the cycles.

Further, although the case in which the N₂ gas is supplied in all processes S11 to S16 is illustrated in the example of FIG. 1, the present disclosure is not limited thereto. For example, the N₂ gas may be supplied at least in purging processes S12, S14, and S16, and the N₂ gas may not be supplied in processes S11, S13, and S15.

(Example Using TiCl₄ Inhibitor)

FIG. 3 is a diagram illustrating another example of a gas supply sequence of a method of forming a TiN film according to an embodiment. In the method of forming the TiN film illustrated in FIG. 3, a plurality of cycles each including processes S31 to S36 are performed. Process S31 is a process of supplying a TiCl₄ inhibitor that inhibits adsorption of TiCl₄. Process S32 is a process of adjusting an adsorption amount of the TiCl₄ inhibitor. Process S33 is a process of supplying the TiCl₄ to a substrate. Process S34 is a process of purging the TiCl₄. Process S35 is a process of supplying NH₃ to the substrate. Process S36 is a process of purging the NH₃.

FIGS. 4A to 4G are process cross-sectional views illustrating another example of a method of forming a TiN film according to an embodiment. FIGS. 4A to 4G illustrate a state in which a Ti—NH_(x) layer is formed on an outermost surface of a concave portion after a plurality of cycles each including processes S31 to S36 are performed after the method of forming the TiN film starts. As illustrated in FIG. 4A, a target substrate 400 on which a TiN film is formed includes an insulating film 401 in which a concave portion 402 is formed. The insulating film 401 may be an SiO₂ film or an Al₂O₃ film.

Process S31 is performed after a process of supplying NH₃ and before a process of supplying TiCl₄. In process S31, as illustrated in FIG. 4A, a TiCl₄ inhibitor 404 that inhibits adsorption of TiCl₄ 406 is supplied to the substrate 400.

Adsorption energy of the TiCl₄ inhibitor 404 on the Ti—NH_(x) layer 403 is preferably higher than adsorption energy of the TiCl₄ 406 on the Ti—NH_(x) layer 403 from the viewpoint that the TiCl₄ inhibitor 404 is more easily adsorbed on a surface of the Ti—NH_(x) layer 403 than the TiCl₄ 406. Examples of such TiCl₄ inhibitor may include boron trifluoride (BF₃), acetic acid (CH₃CO₂H), boron trichloride (BCl₃), hydrogen chloride (HCl), trimethylaluminum (Al(CH₃)₃), sulfuric acid (H₂SO₄), hydrogen bromide (HBr), and aluminum chloride (AlCl₃).

The supply of the TiCl₄ inhibitor 404 may be performed in a dilution gas environment. For example, the TiCl₄ inhibitor 404 may be supplied after an inside of the processing container is replaced with a dilution gas. Further, for example, the dilution gas may be supplied into the processing container together with the TiCl₄ inhibitor 404. In this case, the TiCl₄ inhibitor 404 may be supplied while supplying the dilution gas into the processing container, or the TiCl₄ inhibitor 404 and the dilution gas may be mixed and then the TiCl₄ inhibitor 404 (mixed gas) diluted with the dilution gas may be supplied into the processing container. Examples of the dilution gas may include an inert gas such as N₂ gas, a rare gas, or the like, CO₂ gas, and CO gas. The dilution gas preferably include at least one gas selected from the group consisting of He gas, Ne gas, Ar gas, Kr gas, Xe gas, N₂ gas, CO₂ gas, and CO gas.

In process S31, since the TiCl₄ inhibitor 404 is adsorbed on a surface of the Ti—NH_(x) layer 403 formed in the concave portion 402, it is preferable that the TiCl₄ inhibitor 404 is easily adsorbed on the Ti—NH_(x) layer 403. The TiCl₄ inhibitor having higher adsorption energy on the Ti—NH_(x) layer 403 than that of the TiCl₄ is more easily adsorbed on the surface of the Ti—NH_(x) layer 403 than the TiCl₄. For this reason, as illustrated in FIG. 4B, the TiCl₄ inhibitor is more easily adsorbed on an upper surface 402 c of the concave portion 402 than on a bottom surface 402 a and an inner wall 402 b thereof.

The likelihood of the adsorption of the TiCl₄ inhibitor 404 on the Ti—NH_(x) layer 403 can be predicted, for example, by evaluating an adsorption energy (hereinafter referred to as a “second adsorption energy”) of the TiCl₄ inhibitor 404 on the surface (surface site) of the Ti—NH_(x) layer 403. Further, the “second adsorption energy” is given as a value obtained by subtracting energy before the adsorption from energy when the TiCl₄ inhibitor 404 is adsorbed on the surface site, and a negative value indicates that the adsorption state is stable. Further, the larger the first adsorption energy (negative value), the easier it is for the TiCl₄ inhibitor 404 to be adsorbed on the surface site, and the stronger an adsorption force is. The first adsorption energy is obtained by, for example, a density functional theory (PBE/DNP) using the DMol3 module of the software Materials Studio.

In process S32, a purge gas is supplied into the processing container. Thereby, an amount of the TiCl₄ inhibitor 404 adsorbed on the Ti—NH_(x) layer 403 is adjusted. Specifically, by supplying the purge gas into the processing container, a part of the TiCl₄ inhibitor 404 adsorbed on the surface of the Ti—NH_(x) layer 403 is removed together with the purge gas, and thus the amount of the TiCl₄ inhibitor 404 adsorbed on the Ti—NH_(x) layer 403 is adjusted. In order to prevent the TiCl₄ inhibitor 404 adsorbed on the surface of the Ti—NH_(x) layer 403 from being completely removed, a time of process S32 of adjusting the adsorption amount of the TiCl₄ inhibitor 404 is preferably shorter than a time of process S34 of purging the TiCl₄. Further, when it is not necessary to adjust the amount of the TiCl₄ inhibitor 404 adsorbed on the Ti—NH_(x) layer 403, process S32 may be omitted. Examples of the purge gas may include an inert gas such as N₂ gas, a rare gas, or the like, CO₂ gas, and CO gas. Conditions for supplying the purge gas in process S32 are not particularly limited.

Further, process S32 may be performed by, for example, vacuum suctioning the inside of the processing container without supplying the purge gas into the processing container. Further, process S32 may be performed by supplying the purge gas into the processing container and then vacuum suctioning the inside of the processing container without supplying the purge gas into the processing container. Further, process S32 may be performed by a cycle purge in which the supply of the purge gas and the vacuum suction are repeated.

In process S33, the TiCl₄ 406 is supplied to the concave portion 402, as illustrated in FIG. 4C. In this case, since a greater amount of the TiCl₄ inhibitor 404 is adsorbed on the upper surface 402 c of the concave portion 402 than on the bottom surface 402 a and the inner wall 402 b thereof, a part of the adsorption of the TiCl₄ 406 on the upper surface 402 c of the concave portion 402 is inhibited, as illustrated in FIG. 4D. For this reason, the TiCl₄ 406 is adsorbed on the bottom surface 402 a, the inner wall 402 b, and the upper surface 402 c of the concave portion 402 substantially uniformly.

In process S34, the purge gas is supplied into the processing container. Thereby, as illustrated in FIG. 4B, the TiCl₄ inhibitor 404 adsorbed on the surface of the Ti—NH_(x) layer 403 and the TiCl₄ 406 remaining in the processing container are exhausted and removed from the inside of the processing container. Details of the purge gas and conditions for supplying the purge gas in process S34 may be the same as those in process S32 described above.

In process S35, NH₃ 405 is supplied to the concave portion 402, as illustrated in FIG. 4F. Thereby, as illustrated in FIG. 4G, the TiCl₄ 406 adsorbed on the concave portion 402 and the NH₃ 405 supplied to the concave portion 402 react with each other, and thus a TiN layer 407 is formed.

In process S36, the purge gas is supplied into the processing container. Thereby, the NH₃ 405 remaining in the processing container is removed from the inside of the processing container. Specifically, by supplying the purge gas into the processing container, the NH₃ 405 in the processing container is exhausted together with the purge gas and removed from the inside of the processing container. Details of the purge gas and conditions for supplying the purge gas in process S36 may be the same as those in process S32 described above.

As described above, in the method of forming a TiN film according to the embodiment, before the TiCl₄ 406 is supplied to the concave portion 402, a greater amount of the TiCl₄ inhibitor 404 is adsorbed on an upper portion of the concave portion 402 than on a lower portion thereof. In the case in which a greater amount of the TiCl₄ inhibitor 404 is adsorbed on the upper portion of the concave portion 402 than on the lower portion thereof, when the TiCl₄ 406 is supplied to the concave portion 402, the adsorption of the TiCl₄ 406 onto the upper surface 402 c of the concave portion 402 is inhibited. For this reason, the TiCl₄ 406 is adsorbed on the bottom surface 402 a, the inner wall 402 b, and the upper surface 402 c of the concave portion 402 substantially uniformly. As a result, a thickness of the TiN layer 407 formed by reacting the TiCl₄ 406 and the NH₃ 405 becomes uniform. That is, a conformal TiN film can be formed in the concave portion 402.

Further, the method of forming a TiN film according to the embodiment can be suitably used in, for example, an application for forming a capacitor electrode. In particular, in a semiconductor device having a memory cell such as a DRAM or the like, due to complexity of a trench structure and an increase in aspect ratio of a trench, the step coverage of a TiN film has become an important issue. Therefore, according to the method of forming the TiN film according to the embodiment, ideal conformal film formation with high step coverage and a low loading effect is possible.

Further, although the case in which all of the plurality of cycles include process S31 of supplying the TiCl₄ inhibitor 404 is illustrated in the example of FIG. 3, the present disclosure is not limited thereto. For example, at least a part of the plurality of cycles may include process S31 of supplying the TiCl₄ inhibitor 404. In other words, in at least a part of the plurality of cycles, process S31 of supplying the TiCl₄ inhibitor 404 may be omitted. However, from the viewpoint of obtaining a more conformal TiN film, it is preferable to perform process S31 of supplying the TiCl₄ inhibitor 404 in all the cycles.

Further, although the case in which the N₂ gas is supplied in all processes S31 to S36 is illustrated in the example of FIG. 3, the present disclosure is not limited thereto. For example, the N₂ gas may be supplied at least in the purging processes S32, S34, and S36 and the N₂ gas may not be supplied in processes S31, S33, and S35.

(Example Using NH₃ Inhibitor and TiCl₄ Inhibitor)

FIG. 5 is a diagram illustrating still another example of a gas supply sequence of a method of forming a TiN film according to an embodiment. In the method of forming the TiN film illustrated in FIG. 5, a plurality of cycles each including processes S51 to S58 are performed. Process S51 is a process of supplying a TiCl₄ inhibitor that inhibits adsorption of TiCl₄. Process S52 is a process of adjusting an adsorption amount of the TiCl₄ inhibitor. Process S53 is a process of supplying the TiCl₄ to a substrate. Process S54 is a process of purging the TiCl₄ and the TiCl₄ inhibitor. Process S55 is a process of supplying an NH₃ inhibitor that inhibits adsorption of NH₃. Process S56 is a process of adjusting an adsorption amount of the NH₃ inhibitor. Process S57 is a process of supplying the NH₃ to the substrate. Process S58 is a process of purging the NH₃ and the NH₃ inhibitor.

The method of forming the TiN film illustrated in FIG. 5 includes process S51 of supplying the TiCl₄ inhibitor and process S55 of supplying the NH₃ inhibitor. Process S51 of supplying the TiCl₄ inhibitor is performed after process S57 of supplying the NH₃ and before process S53 of supplying the TiCl₄. Process S55 of supplying the NH₃ inhibitor is performed after process S53 of supplying the TiCl₄ and before process S57 of supplying the NH₃.

Further, process S52 may be the same as process S32 described above, process S53 may be the same as process S33 described above, and process S54 may be the same as process S34 described above. Further, process S56 may be the same as process S12 described above, process S57 may be the same as process S13 described above, and process S58 may be the same as process S14 described above.

As described above, in the method of forming a TiN film according to the embodiment, before the NH₃ is supplied to the concave portion, a greater amount of the NH₃ inhibitor is adsorbed on an upper portion of the concave portion than on a lower portion thereof. In the case in which a greater amount of the NH₃ inhibitor is adsorbed on the upper portion of the concave portion than on the lower portion thereof, when the NH₃ is supplied to the concave portion, the adsorption of the NH₃ onto the upper surface of the concave portion is inhibited. For this reason, the NH₃ is adsorbed on the bottom surface, the inner wall, and the upper surface of the concave portion substantially uniformly. As a result, a thickness of the TiN layer formed by reacting the NH₃ and the TiCl₄ becomes uniform. That is, a conformal TiN film can be formed in the concave portion.

Further, in the method of forming a TiN film according to the embodiment, before the TiCl₄ is supplied to the concave portion, a greater amount of the TiCl₄ inhibitor is adsorbed on an upper portion of the concave portion than on a lower portion thereof. In the case in which a greater amount of the TiCl₄ inhibitor is adsorbed on the upper portion of the concave portion than on the lower portion thereof, when the TiCl₄ is supplied to the concave portion, the adsorption of the TiCl₄ onto the upper surface of the concave portion is inhibited. For this reason, the TiCl₄ is adsorbed on the bottom surface, the inner wall, and the upper surface of the concave portion substantially uniformly. As a result, a thickness of the TiN layer formed by reacting the NH₃ and the TiCl₄ becomes uniform. That is, a conformal TiN film can be formed in the concave portion.

Further, the method of forming a TiN film according to the embodiment can be suitably used in, for example, an application for forming a capacitor electrode. In particular, in a semiconductor device having a memory cell such as a DRAM or the like, due to complexity of the trench structure and an increase in aspect ratio of a trench, the step coverage of the TiN film has become an important issue. Therefore, according to the method of forming the TiN film according to the embodiment, ideal conformal film formation with high step coverage and a low loading effect is possible.

Further, although the case in which all of the plurality of cycles include process S51 of supplying the TiCl₄ inhibitor and process S55 of supplying the NH₃ inhibitor is illustrated in the example of FIG. 5, the present disclosure is not limited thereto. For example, at least a part of the plurality of cycles may include process S51 of supplying the TiCl₄ inhibitor. Further, at least a part of the plurality of cycles may include process S55 of supplying the NH₃ inhibitor. In other words, in at least a part of the plurality of cycles, process S51 of supplying the TiCl₄ inhibitor may be omitted. Further, in at least a part of the plurality of cycles, process S55 of supplying the NH₃ inhibitor may be omitted. However, from the viewpoint of obtaining a more conformal TiN film, it is preferable to perform process S51 of supplying the TiCl₄ inhibitor and process S55 of supplying the NH₃ inhibitor in all the cycles.

Further, although the case in which the N₂ gas is supplied in all processes S51 to S58 is illustrated in the example of FIG. 5, the present disclosure is not limited thereto. For example, the N₂ gas may be supplied at least in the purging processes S52, S54, S56, and S58 and the N₂ gas may not be supplied in processes S51, S53, S55, and S57.

[Film-Forming Device]

A film-forming device used in the method of forming a TiN film according to an embodiment will be described using a single-wafer device as an example. FIG. 6 is a diagram illustrating an example of a film-forming device used in a method of forming a TiN film according to an embodiment.

As illustrated in FIG. 6, a film-forming device 100 includes a processing container 1, a stage 2, a showerhead 3, an exhaust unit 4, a gas supply mechanism 5, and a controller 9.

The processing container 1 is made of metal such as aluminum or the like and has a substantially cylindrical shape. The processing container 1 accommodates a wafer W. A loading/unloading port 11 for loading or unloading the wafer W is formed in a sidewall of the processing container 1, and the loading/unloading port 11 is opened or closed by a gate valve 12. An annular exhaust duct 13 having a rectangular cross section is provided on a main body of the processing container 1. A slit 13 a is formed along an inner circumferential surface of the exhaust duct 13. An exhaust port 13 b is formed in an outer wall of the exhaust duct 13. A ceiling wall 14 is provided on an upper surface of the exhaust duct 13 to close an upper opening of the processing container 1. A space between the exhaust duct 13 and the ceiling wall 14 is airtightly sealed with a seal ring 15.

The stage 2 supports the wafer W horizontally in the processing container 1. The stage 2 is formed in a disc shape having a size corresponding to the wafer W and is supported by a support member 23. The stage 2 is made of a ceramic material such as AIN or a metal material such as aluminum, a nickel alloy, or the like, and a heater 21 for heating the wafer W is embedded therein. The heater 21 is supplied with electricity from a heater power supply (not illustrated) to generate heat. Then, the wafer W is controlled to a predetermined temperature by controlling an output of the heater 21 using a temperature signal of a thermocouple (not illustrated) provided in the vicinity of an upper surface of the stage 2. A cover member 22, which is formed of ceramic such as alumina, is provided on the stage 2 to cover an outer circumferential region of the upper surface of the stage 2 and side surfaces thereof.

The support member 23 for supporting the stage 2 is provided on a bottom surface of the stage 2. The support member 23 extends from the center of the bottom surface of the stage 2 to a lower side of the processing container 1 to pass through a hole formed in a bottom wall of the processing container 1, and a lower end of the support member 23 is connected to a lifting mechanism 24. The lifting mechanism 24 causes the stage 2 to move up and down via the support member 23 between a processing position illustrated in FIG. 6 and a transfer position where the wafer W can be transferred which is indicated by an alternate long and two short dashes line below the processing position. A flange 25 is attached to the support member 23 below the processing container 1, and a bellows 26 that separates an atmosphere inside the processing container 1 from outside air and expands and contracts as the stage 2 moves up and down is provided between a bottom surface of the processing container 1 and the flange 25.

In the vicinity of the bottom surface of the processing container 1, three wafer support pins 27 (only two are illustrated) are provided to protrude upward from a lifting plate 27 a. The wafer support pins 27 are raised and lowered via the lifting plate 27 a by a lifting mechanism 28 provided below the processing container 1. The wafer support pins 27 are inserted into a through hole 2 a provided in the stage 2 placed at the transfer position, and can be raised or lowered with respect to the upper surface of the stage 2. The wafer W is transferred between a transfer mechanism (not illustrated) and the stage 2 by raising and lowering the wafer support pins 27.

The showerhead 3 supplies a processing gas into the processing container 1 in the form of a shower. The showerhead 3 is made of a metal, is provided to face the stage 2, and has substantially the same diameter as the stage 2. The showerhead 3 has a main body portion 31 fixed to the ceiling wall 14 of the processing container 1, and a shower plate 32 connected under the main body portion 31 to be connected. A gas diffusion space 33 is formed between the main body portion 31 and the shower plate 32, and gas introduction holes 36 a to 36 d are provided in the gas diffusion space 33 to pass through the ceiling wall 14 of the processing container 1 and the center of the main body portion 31. An annular projection 34 protruding downward is formed on the periphery of the shower plate 32. Gas discharge holes are formed in an inner flat surface of the annular projection 34. In the state in which the stage 2 is present at the processing position, a processing space 38 is formed between the stage 2 and the shower plate 32, and an annular gap 39 is formed by the proximity of an upper surface of the cover member 22 and the annular projection 34.

The exhaust unit 4 exhausts an inside of the processing container 1. The exhaust unit 4 includes an exhaust pipe 41 connected to the exhaust port 13 b, and an exhaust mechanism 42 which has a vacuum pump, a pressure control valve, or the like connected to the exhaust pipe 41. At the time of processing, the gas in the processing container 1 reaches the exhaust duct 13 through the slit 13 a and is exhausted from the exhaust duct 13 through the exhaust pipe 41 by the exhaust mechanism 42.

The gas supply mechanism 5 supplies the processing gas into the processing container 1. The gas supply mechanism 5 includes a TiCl₄ gas supply source 51 a, an N₂ gas supply source 52 a, an NH₃ gas supply source 53 a, an N₂ gas supply source 54 a, a TiCl₄ inhibitor supply source 55 a, an N₂ gas supply source 56 a, an NH₃ inhibitor supply source 57 a, and an N₂ gas supply source 58 a.

The TiCl₄ gas supply source 51 a supplies TiCl₄ gas into the processing container 1 via a gas supply line 51 b. A flow rate controller 51 c and a valve 51 e are connected to the gas supply line 51 b from an upstream side. A downstream side of the valve 51 e of the gas supply line 51 b is connected to the gas introduction hole 36 a. The supply and stop of the TiCl₄ gas from the TiCl₄ gas supply source 51 a into the processing container 1 are performed by opening and closing the valve 51 e.

The N₂ gas supply source 52 a supplies N₂ gas, which is a carrier gas of the TiCl₄ gas, into the processing container 1 via a gas supply line 52 b. A flow rate controller 52 c and a valve 52 e are connected to the gas supply line 52 b from an upstream side. A downstream side of the valve 52 e of the gas supply line 52 b is connected to the gas supply line 51 b. The N₂ gas supplied from the N₂ gas supply source 52 a is continuously supplied into the processing container 1 during, for example, a film forming process. The supply and stop of the N₂ gas from the N₂ gas supply source 52 a into the processing container 1 are performed by opening and closing the valve 52 e.

The NH₃ gas supply source 53 a supplies NH₃ gas into the processing container 1 via a gas supply line 53 b. A flow rate controller 53 c and a valve 53 e are connected to the gas supply line 53 b from an upstream side. A downstream side of the valve 53 e of the gas supply line 53 b is connected to the gas introduction hole 36 b. The supply and stop of the NH₃ gas from the NH₃ gas supply source 53 a into the processing container 1 are performed by opening and closing the valve 53 e.

The N₂ gas supply source 54 a supplies N₂ gas, which is a carrier gas of the NH₃ gas, into the processing container 1 via a gas supply line 54 b. A flow rate controller 54 c and a valve 54 e are connected to the gas supply line 54 b from an upstream side. A downstream side of the valve 54 e of the gas supply line 54 b is connected to the gas supply line 53 b. The N₂ gas supplied from the N₂ gas supply source 54 a is continuously supplied into the processing container 1 during, for example, a film forming process. The supply and stop of the N₂ gas from the N₂ gas supply source 54 a into the processing container 1 are performed by opening and closing the valve 54 e.

The TiCl₄ inhibitor supply source 55 a supplies a TiCl₄ inhibitor into the processing container 1 via a gas supply line 55 b. A flow rate controller 55 c and a valve 55 e are connected to the gas supply line 55 b from an upstream side. A downstream side of the valve 55 e of the gas supply line 55 b is connected to the gas introduction hole 36 d. The supply and stop of the TiCl₄ inhibitor from the TiCl₄ inhibitor supply source 55 a into the processing container 1 are performed by opening and closing the valve 55 e.

The N₂ gas supply source 56 a supplies N₂ gas, which is a carrier gas of the TiCl₄ inhibitor, into the processing container 1 via a gas supply line 56 b. A flow rate controller 56 c and a valve 56 e are connected to the gas supply line 56 b from an upstream side. A downstream side of the valve 56 e of the gas supply line 56 b is connected to the gas supply line 55 b. The N₂ gas supplied from the N₂ gas supply source 56 a is continuously supplied into the processing container 1 during, for example, a film forming process. The supply and stop of the N₂ gas from the N₂ gas supply source 56 a into the processing container 1 are performed by opening and closing the valve 56 e.

The NH₃ inhibitor supply source 57 a supplies an NH₃ inhibitor into the processing container 1 via a gas supply line 57 b. A flow rate controller 57 c and a valve 57 e are connected to the gas supply line 57 b from an upstream side. A downstream side of the valve 57 e of the gas supply line 57 b is connected to the gas introduction hole 36 c. The supply and stop of the NH₃ inhibitor from the NH₃ inhibitor supply source 57 a into the processing container 1 are performed by opening and closing the valve 57 e.

The N₂ gas supply source 58 a supplies N₂ gas, which is a carrier gas of the NH₃ inhibitor, into the processing container 1 via a gas supply line 58 b. A flow rate controller 58 c and a valve 58 e are connected to the gas supply line 58 b from an upstream side. A downstream side of the valve 58 e of the gas supply line 58 b is connected to the gas supply line 57 b. The N₂ gas supplied from the N₂ gas supply source 58 a is continuously supplied into the processing container 1 during, for example, a film forming process. The supply and stop of the N₂ gas from the N₂ gas supply source 58 a into the processing container 1 are performed by opening and closing the valve 58 e.

The controller 9 is, for example, a computer, and includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), an auxiliary storage device, and the like. The CPU operates based on a program, which is stored in a ROM or an auxiliary storage device, and controls the operation of the film-forming device 100. The controller 9 may be provided inside the film-forming device 100 or may be provided outside the film-forming device 100. When the controller 9 is provided outside the film-forming device 100, the controller 9 can control the film-forming device 100 using a wired or wireless communication means.

[Operation of Film-Forming Device]

An example of the operation of the film-forming device 100 will be described. Further, at the time of starting, the inside of the processing container 1 has a vacuum atmosphere due to the exhaust unit 4. Further, the stage 2 has moved to the transfer position.

The controller 9 opens the gate valve 12. Here, the wafer W is placed on the wafer support pins 27 by an external transfer mechanism (not illustrated). When the transfer mechanism comes out of the loading/unloading port 11, the controller 9 closes the gate valve 12.

The controller 9 controls the lifting mechanism 24 to move the stage 2 to the processing position. In this case, by raising the stage 2, the wafer W placed on the wafer support pins 27 is placed on a mounting surface of the stage 2.

At the processing position, the controller 9 operates the heater 21 and controls the gas supply mechanism 5 to supply a processing gas such as TiCl₄ gas, NH₃ gas, a TiCl₄ inhibitor, an NH₃ inhibitor, or the like or a carrier gas such as N₂ gas or the like, into the processing container 1. Thereby, a TiN film is formed on the wafer W. The gas after the processing is exhausted by the exhaust mechanism 42 via the exhaust pipe 41.

When the predetermined processing is completed, the controller 9 controls the lifting mechanism 24 to move the stage 2 to the transfer position. At this time, head portions of the wafer support pins 27 protrude from the mounting surface of the stage 2, and the wafer W is lifted from the mounting surface of the stage 2.

The controller 9 opens the gate valve 12. Here, the wafer W placed on the wafer support pins 27 is unloaded by the external transfer mechanism. When the transfer mechanism comes out of the loading/unloading port 11, the controller 9 closes the gate valve 12.

As described above, according to the film-forming device 100 illustrated in FIG. 6, a TiN film can be formed on the wafer W.

[Simulation Result]

Using the DMol3 module of the software Materials Studio, adsorption energy of an NH₃ inhibitor on a surface of a TiCl_(x) layer and adsorption energy of a TiCl₄ inhibitor on a surface of a Ti—NH_(x) layer were calculated by a density functional theory (PBE/DNP).

FIG. 7 is a diagram illustrating an example of simulation results of adsorption energy of an NH₃ inhibitor. FIG. 7 illustrates calculation results of adsorption energy of acetone, DMSO, THF, and pyridine on a surface of a TiCl_(x) layer in order from the left side.

As illustrated in FIG. 7, the adsorption energies of acetone, DMSO, THF, and pyridine were higher than -1.1 eV.

FIG. 8 is a diagram illustrating an example of simulation results of adsorption energy of a TiCl₄ inhibitor. FIG. 8 illustrates calculation results of adsorption energy of Ti(OC₂H₅)₄, B(OCH₃),₃, Si(OC₂H₅)₄, TiCl₄, boron trifluoride (BF₃), acetic acid (CH₃CO₂H) , boron trichloride (BCl₃), hydrogen chloride (HCl), trimethylaluminum (Al(CH₃)₃), sulfuric acid (H₂SO₄), hydrogen bromide (HBr), and aluminum chloride (AlCl₃) on a surface of a Ti—NH_(x) layer in order from the left side.

As illustrated in FIG. 8, the adsorption energies of Ti(OC₂H₅)₄, B(OCH₃)₃, and Si(OC₂H₅)₄ are in a range of −0.5 eV to −1.0 eV and were lower than the adsorption energy of the TiCl₄. On the other hand, the adsorption energies of BF₃, CH₃CO₂H, BCl₃, HCl, Al(CH₃)₃, H₂SO₄, HBr, and AlCl₃ are in a range of −1.0 eV to −3.0 eV and were higher than the adsorption energy of the TiCl₄.

When a TiN film is formed using an ALD process, it is preferable to use a TiCl₄ inhibitor containing BF₃, CH₃CO₂H, BCl₃, HCl, Al(CH₃)₃, H₂SO₄, HBr, and AlCl₃ having higher adsorption energy than TiCl₄. Thereby, an inhibitor can be easily adsorbed on a surface of a Ti—NH_(x) layer.

The embodiment disclosed here should be considered exemplary and not restrictive in any respect. The above embodiment may be omitted, replaced, or modified in various forms without departing from the scope of the appended claims and their gist.

Although the case in which a film-forming device is a single-wafer device that processes wafers one by one has been described in the above embodiment, the present disclosure is not limited thereto. For example, the film-forming device may be a batch type device that processes a plurality of wafers at once.

This international application claims priority based on Japanese Patent Application No. 2019-174644 filed on Sep. 25, 2019, and the entire contents of this application shall be incorporated into this international application.

DESCRIPTION OF REFERENCE NUMERALS

-   1: processing container -   5: gas supply mechanism -   9: controller -   100: film-forming device 

1. A method for manufacturing a semiconductor device including a TiN film, the method comprising: supplying TiCl₄ gas to a substrate; purging the TiCl₄ gas; supplying NH₃ gas to the substrate; purging the N₃ gas; and supplying an inhibitor that inhibits adsorption of TiCl₄ or NH₃ to the substrate, wherein a plurality of cycles each including the supplying the TiCl₄ gas, the purging the TiCl₄ gas, the supplying the NH₃ gas, and the purging the NH₃ gas are performed, at least a part of the plurality of cycles includes the supplying the inhibitor, and after the supplying the inhibitor is performed, the supplying the TiCl₄ gas or the supplying the NH₃ gas is performed without purging the inhibitor, or, after purging the inhibitor for a shorter time than the purging the TiCl₄ gas or the purging the NH₃ gas, the supplying the TiCl₄ gas or the supplying the NH₃ gas is performed.
 2. The method of claim 1, wherein the supplying the inhibitor includes supplying an NH₃ inhibitor that inhibits adsorption of the NH₃ between the supplying the TiCl₄ gas and the supplying the NH₃ gas.
 3. The method of claim 2, wherein the NH₃ inhibitor includes an organic compound having at least one of a C═O bond, an S═O bond, a CN ring, and a CO ring.
 4. The method of claim 3, wherein the NH₃ inhibitor includes acetone, dimethyl sulfoxide (DMSO), THF, pyridine, or a derivative thereof.
 5. The method of claim 1, wherein the supplying the inhibitor includes supplying a TiCl₄ inhibitor that inhibits adsorption of the TiCl₄ between the supplying the NH₃ gas and the supplying the TiCl₄ gas.
 6. The method of claim 5, wherein adsorption energy of the TiCl₄ inhibitor on a surface of a Ti—NH_(x) layer is higher than adsorption energy of the TiCl₄ on the surface of the Ti—NH_(x) layer.
 7. The method of claim 6, wherein the TiCl₄ inhibitor includes BF₃, CH₃CO₂H, BCl₃, HCl, Al(CH₃)₃, H₂SO₄, HBr, or AlCl₃.
 8. The method of claim 1, wherein a concave portion is formed in the substrate.
 9. The method of claim 8, wherein, in the supplying the inhibitor, a greater amount of the inhibitor is adsorbed on an upper portion of the concave portion than on a lower portion thereof.
 10. A film-forming device comprising: a processing container configured to accommodate a substrate; a gas supply mechanism configured to supply gas into the processing container; and a controller, wherein the controller controls the gas supply mechanism to perform: supplying TiCl₄ gas to the substrate; purging the TiCl₄ gas; supplying NH₃ gas to the substrate; purging the NH₃ gas; and supplying an inhibitor that inhibits adsorption of TiCl₄ or NH₃ to the substrate, wherein the controller controls the gas supply mechanism to perform a plurality of cycles each including the supplying the TiCl₄ gas, the purging the TiCl₄ gas, the supplying the NH₃ gas, and the purging the NH₃ gas, wherein at least a part of the plurality of cycles includes the supplying the inhibitor, and wherein the controller controls the gas supply mechanism to, after the supplying the inhibitor is performed, perform the supplying the TiCl₄ gas or the supplying the NH₃ gas without purging the inhibitor, or, after purging the inhibitor for a shorter time than the purging the TiCl₄ gas or the purging the NH₃ gas, perform the supplying the TiCl₄ gas or the supplying the NH₃ gas. 